As portable or wearable devices become more and more popular and advanced, it is common for portable devices to be equipped with a high-performance processor, diverse sensors, and ubiquitous networking so as to offer functionalities of positioning and navigation. As a result, a number of navigation applications on the portable device have been developed.
In order to obtain the location of the portable device, a number of outdoor and indoor positioning methods may be utilized. For example, a global positioning system (GPS) unit may be employed for outdoor positioning. For indoor positioning, the portable device may be configured to detect pre-deployed indoor positioning infrastructure, like QR code or wireless sensor network (WSN), to obtain a relative indoor location. But, these multilateration-based outdoor and indoor positioning methods above always suffer from electromagnetic interference and infrastructure cost. Based on the principle of dead reckoning, the inertial positioning device using an inertial measurement unit (IMU) to determine the displacement of the user relative to an initial position is a better alternative. More importantly, it never suffers from electromagnetic interference and infrastructure cost.
However, some inevitable faults in the inertial positioning device need to be solved at first, for example, the error rate of the walk detection and the error-accumulation nature of the inertial positioning device. Especially, when the portable device is rotated or shaken by the user staying at the same location, the inertial positioning device tends to misdetect the walk state of the user and misestimate the distance of the displacement.